Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Polymerase chain reaction is used in DNA amplification Reason (R): The ampicillin resistant gene is used as a selectable marker to check transformation In the light of the above statements, choose the correct answer from the options given below :
(A)(A) is not correct but (R) is correct
(B)Both (A) and (R) are correct and (R) is the correct explanation of (A)

(C)Both (A) and (R) are correct but (R) is not the correct explanation of `` ( A ) ``
(D)(A) is correct but (R) is not correct